We propose a hierarchical blockchain-based platform for ensuring the integrity of smart city Internet-of-Things (IoT) data and blockchain interoperability in this paper. The well-defined structural hierarchy of managing organizations in a smart city face several data management issues. The integration of emerging technologies, such as (IoT), has introduced more complexity to data maintenance in the smart city. At present, cloud-based information systems have become the norm for managing IoT data. Due to the centralized administrative control, the cloud-based information management is untrusted. Hence, it fails to guarantee the integrity of IoT data and traceability of operations to achieve transparency within the smart city organizations. Adoption of blockchain-based information systems can be viable solution to address these challenges. However, it introduces a new challenge of interoperability of transactions among different smart city organizations. In this paper, we introduce a decentralized hierarchy of blockchains, named Blockchain-of-Blockchains (BoBs), for ensuring data integrity and blockchain interoperability at the same time. We implement the proposed concept using Hyperledger Fabric and Ethermint as a proof-of-concept for evaluating the performance of the proposed concept.

在本文中，我们提出了一个基于分层区块链的平台，以确保智慧城市物联网 (IoT) 数据的完整性和区块链的互操作性。智慧城市中管理组织的定义明确的结构层次结构面临着几个数据管理问题。（物联网）等新兴技术的集成为智慧城市中的数据维护带来了更多复杂性。目前，基于云的信息系统已成为管理物联网数据的规范。由于集中管理控制，基于云的信息管理是不可信的。因此，它无法保证物联网数据的完整性和运营的可追溯性，以实现智慧城市组织内的透明度。采用基于区块链的信息系统可能是应对这些挑战的可行解决方案。然而，它引入了不同智慧城市组织之间交易互操作性的新挑战。在本文中，我们介绍了一个分散的区块链层次结构，命名为Blockchain-of-Blockchains (BoBs)，用于同时确保数据完整性和区块链互操作性。我们使用 Hyperledger Fabric 和 Ethermint 作为概念验证来实现提议的概念，以评估提议的概念的性能。